Genetic diversity and phylogenetic relationships among East Asian common wheat (Triticum aestivum L.) populations, revealed by the analysis of five isozymes

Genetic diversity and genetic structure of East Asian wheat populations were studied based on the analysis of five isozymes using 324 wheat landraces. Gene diversity value calculated from the frequency of 31 isozyme bands varied within China, being higher in the western part than in the eastern part. Twenty populations of wheat landraces were classified into three major groups by cluster analysis, and wheat populations from the neighboring areas were clustered together. The first group comprised most of the populations from China (West), though two populations from Xinjiang and Gansu & Ningxia were rather distantly related to the populations from Tibet, Sichuan (West) and Yunnan. These results indicated the transmission of wheat from Nepal to the Tibetan area of China. The second group included the northern populations, from Mongolia to Japan (Northeast), indicating the transmission of wheat through the northern route of the "Silk road". The third group consisted of wheat populations from Shaanxi, China (Southeast) and Japan (Southwest). Wheat population from Shaanxi was also related to the population from Hebei and Gansu & Ningxia, strongly suggesting the transmission of wheat through the "Silk road": Xinjiang-Gansu & Ningxia-Shaanxi-Shandong. In addition, in the eastern part of China, genetic differentiation among wheat populations from northern and southern parts was observed, and a similar geographical differentiation was also recorded in Korea and Japan.